The scope of the possible breach is unknown, but credit card giant MasterCard also confirmed Saturday that it has sent alerts to several banks notifying them that some of its customers may be affected and that it is investigating the possible leak.

“The Department of Motor Vehicles has been alerted by law enforcement authorities to a potential security issue within its credit card processing services,” according to a DMV statement issued in response to reports of MasterCard’s investigation. “There is no evidence at this time of a direct breach of the DMV’s computer system. However, out of an abundance of caution and in the interest of protecting the sensitive information of California drivers, the DMV has opened an investigation into any potential security breach in conjunction with state and federal law enforcement.”

“In its investigation, the department is performing a forensic review of its systems and seeking information regarding any potential breach from both the external vendor that processes the DMV’s credit card transactions and the credit card companies themselves.”

The possible breach appears to be limited to online transactions, made without a physical card swipe, between Aug. 2, 2013, and Jan. 31 of this year.

MasterCard spokesman Seth Eisen said in an email that the breach did not originate with MasterCard’s systems, and that the company is encouraging all customers to review their recent transactions and to contact their card issuer for any assistance.

The breach was first reported by blogger Brian Krebs, who broke the story about Target’s massive credit card breach last year, citing sources at five banks who confirmed lists had been received from MasterCard of customers possibly affected. Krebs reported that the information stolen appears to include the card number, expiration date and three-digit security code on the back of each card. It is unknown if other sensitive data, including driver’s license numbers, could also be compromised.

According to Krebs, one bank confirmed to him that about 1,000 of its customers were on the list it received from MasterCard.